<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>06-仿新浪注册页面</title>
    <style>
        div {
            width :600px;
            margin : 100px auto;
        }

        .message {
            display: inline-block;
            font-size: 12px;
            color:#999;
            background: url(./images/mess.png) no-repeat left center;
            padding-left: 20px;
        }

        .wrong {
            color :red;
            background-image: url(./images/wrong.png);
        }
        .right {
            color :green;
            background-image: url(./images/right.png);
        }
    </style>
</head>
<body>
    <div class="register">
        <input type="password" class="ipt" name="" id="">
        <p class="message">请输入4~8位密码</p>
    </div>
    <script>
        // 需求：表单失去焦点，如果密码不合法，则 p 标签类样式更改，内容也相应变化
        //      如何合法，也进行相应变化
        let input = document.querySelector('input');
        let p = document.querySelector('P');
        input.onblur = function(){
            let value = input.value;
            if(value.length >= 4 && value.length <= 8){
                p.className = 'message right';
                p.innerHTML = '密码合法';
            } else{
                p.className = 'message wrong';
                p.innerHTML = '密码不合法';
            }
        }
    </script>
</body>
</html>